Technical Field
The present invention relates to a heat spreading module suitable for dissipating heat of an electronic element which is a heat-generating body in a portable information terminal such as a smartphone or a tablet personal computer or an electronic device.
Description of the Related Art
In a portable information terminal or an electronic device, the amount of heat generation is increasing with increase in the amount of information processing, and need for suppressing rise in the temperature of an electronic element such as CPU is increasing in order to prevent malfunction due to heat, reduction in an information processing speed, or the like. Furthermore, in the portable electronic device, thickness reduction, weight reduction, and miniaturization are required in order to achieve satisfactory portability.
Conventionally, a portable terminal device formed so as to alleviate a heat spot due to heat generated by an integrated circuit has been described in Japanese Unexamined Patent Application, First Publication No. 2014-22798 A.
In a device described in Japanese Unexamined Patent Application, First Publication No. 2014-22798 A, an integrated circuit is disposed at an upper position of a casing, a battery is disposed at a lower position of the casing, and a graphite sheet attached to a back surface of a display panel is disposed so as to be able to transfer heat to the integrated circuit and the battery. Heat of the integrated circuit is diffused into the battery by the graphite sheet, and a heat spot is thereby alleviated.
In the structure described in Japanese Unexamined Patent Application, First Publication No. 2014-22798 A, a graphite sheet is laminated and disposed on a substrate provided with an integrated circuit or a battery, and therefore the graphite sheet is preferably thin for making a portable terminal device thinner or smaller. However, even though the graphite sheet has a high thermal conductivity, the amount of thermal conduction is reduced by reduction in thickness of the graphite sheet. Therefore, a heat dissipation function is deteriorated and the temperature of a heat spot is raised with reduction in thickness of the graphite sheet. Heat transfer (dissipation) by the graphite sheet occurs uniformly in the directions with a portion in contact with an integrated circuit as the center. That is, in the structure, the amount of heat transfer or a path for heat transfer cannot be selected. Therefore, even when there is a portion effective for cooling an integrated circuit such as a portion having a low temperature and a large heat capacity, for example, heat transfer to the portion cannot be promoted. That is, there is much room for improvement.